Endoscope apparatus

ABSTRACT

An endoscope apparatus includes an image pickup section equipped with a color separation section that picks up an image of returning light from a subject illuminated by an illumination section, an emphasis processing section that performs emphasis processing on sharpness of an image signal generated from the output signal of the image pickup section and a storage section that stores information for modifying processing contents of the emphasis processing, wherein the storage section stores information for setting image signals to be subjected to emphasis processing in first and second observation modes in which images are picked up under illumination of white light and narrow band light respectively to a luminance signal and a color difference signal, and the emphasis processing section performs emphasis processing on the luminance signal with a greater emphasis characteristic than the color difference signal over an entire frequency domain.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation application of PCT/JP2011/063064filed on Jun. 7, 2011 and claims benefit of Japanese Application No.2010-146537 filed in Japan on Jun. 28, 2010, the entire contents ofwhich are incorporated herein by this reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an endoscope apparatus that performsimage processing on image pickup means mounted on an endoscope.

2. Description of the Related Art

In recent years, electronic endoscopes equipped with image pickup meanshave been widely used in various endoscope inspections or the like.

When an endoscope inspection is performed, such endoscope apparatusesare available as a simultaneous endoscope apparatus that picks up acolor image using an electronic endoscope equipped with an image pickupdevice provided with a color filter under illumination of white lightand a frame sequential endoscope apparatus that picks up an image underframe sequential illuminating light of R, G and B using an electronicendoscope equipped with a monochrome image pickup device, and theseendoscope apparatuses have different signal processing systems (imageprocessing systems).

As a first conventional example of the endoscope apparatus using anelectronic endoscope equipped with an image pickup device provided witha color filter, Japanese Patent Publication No. 4009626 discloses anendoscope apparatus equipped with an emphasis circuit that emphasizescontours or a structure for only luminance signals.

On the other hand, as a second conventional example of the endoscopeapparatus using an electronic endoscope equipped with an image pickupdevice provided with a color filter, Japanese Patent ApplicationLaid-Open Publication No. 2006-61621 discloses an endoscope apparatusthat performs emphasis processing on luminance signals and colordifference signals.

SUMMARY OF THE INVENTION

An endoscope apparatus according to an aspect of the present inventionincludes an image pickup section equipped with a color separationsection that color-separates and receives returning light of lightradiated onto a subject by an illumination section to pick up an imageof the subject, an emphasis processing section that performs emphasisprocessing on sharpness of an image signal based on the image pickupsection, a storage section that stores information for modifyingprocessing contents of the emphasis processing section according tospectral characteristics of the returning light incident on the imagepickup section which differ depending on a type of the image pickupsection and an observation mode and a control section that performscontrol of modifying the processing contents of the emphasis processingsection based on the information of the storage section, wherein thestorage section sets, when the observation mode is a first observationmode in which image pickup is performed under illumination of whitelight, an image signal to be subjected to emphasis processing by theemphasis processing section to a luminance signal and two colordifference signals, and stores, when the observation mode is a secondobservation mode in which image pickup is performed under illuminationof narrow band illuminating light, information for setting an imagesignal to be subjected to emphasis processing by the emphasis processingsection to a luminance signal and one color difference signal, and inthe first observation mode and the second observation mode, the emphasisprocessing section performs emphasis processing on the luminance signalin the image signal with a greater emphasis characteristic than thecolor difference signal in the image signal over an entire frequencydomain.

An endoscope apparatus according to another aspect of the presentinvention includes an image pickup section equipped with a colorseparation section that color-separates and receives returning light oflight radiated onto a subject by an illumination section to pick up animage of the subject, an emphasis processing section that performsemphasis processing on sharpness of an image signal based on the imagepickup section, a storage section that stores information for modifyingprocessing contents of the emphasis processing section according tospectral characteristics of the returning light incident on the imagepickup section which differ depending on a type of the image pickupsection and an observation mode and a control section that performscontrol of modifying the processing contents of the emphasis processingsection based on the information of the storage section, wherein thestorage section sets, when the observation mode is a first observationmode in which image pickup is performed under illumination of whitelight, an image signal to be subjected to emphasis processing by theemphasis processing section to a luminance signal and two colordifference signals, and stores, when the observation mode is a secondobservation mode in which image pickup is performed under illuminationof narrow band illuminating light, information for setting an imagesignal to be subjected to emphasis processing by the emphasis processingsection to a luminance signal and one color difference signal, and inthe first observation mode and the second observation mode, the emphasisprocessing section performs emphasis processing on the color differencesignal in the image signal with a smaller emphasis characteristic thanthe luminance signal in the image signal in a frequency domain on a highfrequency side having a higher frequency.

An endoscope apparatus according to a further aspect of the presentinvention includes an image pickup section equipped with a colorseparation section that color-separates and receives returning light oflight radiated onto a subject by an illumination section to pick up animage of the subject, an emphasis processing section that performsemphasis processing on sharpness of an image signal based on the imagepickup section, a storage section that stores information for modifyingprocessing contents of the emphasis processing section according tospectral characteristics of the returning light incident on the imagepickup section which differ depending on a type of the image pickupsection and an observation mode and a control section that performscontrol of modifying the processing contents of the emphasis processingsection based on the information of the storage section, wherein thestorage section stores information for setting an image signal to besubjected to emphasis processing by the emphasis processing section tocolor signals of R, G and B according to an array structurecorresponding to unit pixels of a plurality of filter elements havingdifferent transmission characteristics and making up the colorseparation section when the observation mode is a first observation modein which image pickup is performed under illumination of white light andsetting the image signal so as to emphasize the color signal of G morethan the color signal of B to be subjected to emphasis processing by theemphasis processing section when the observation mode is a secondobservation mode in which image pickup is performed under illuminationof narrow band illuminating light.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram illustrating a configuration of an endoscopeapparatus according to a first embodiment of the present invention;

FIG. 2 is a characteristic diagram illustrating an example of spectralcharacteristics of a narrow band filter;

FIG. 3 is a diagram illustrating a configuration of a filter array of acolor separation filter provided in a solid image pickup device;

FIG. 4 is a diagram illustrating an example of emphasis characteristicsfor luminance and color difference signals of an emphasis circuit;

FIG. 5 is a flowchart for illustrating main operations according to thefirst embodiment;

FIG. 6 is a diagram illustrating an example of emphasis characteristicsof an emphasis circuit according to a modification example;

FIG. 7 is a block diagram illustrating a configuration of an endoscopeapparatus in a modification example of the first embodiment;

FIG. 8 is a block diagram illustrating a configuration of an endoscopeapparatus according to a second embodiment of the present invention;

FIG. 9 is a diagram illustrating a filter array of a color filteraccording to the second embodiment;

FIG. 10 is a diagram illustrating a configuration of a periphery of adouble CCD image pickup section provided at a distal end portion of theendoscope;

FIG. 11 is a diagram illustrating a filter array of a color filter usedfor the double CCD image pickup section;

FIG. 12 is a block diagram illustrating a configuration of an endoscopeapparatus according to a third embodiment;

FIG. 13 is a diagram illustrating color separation into three primarycolors by a triple CCD image pickup section;

FIG. 14 is a diagram illustrating an example of setting emphasischaracteristics with respect to an emphasized signal emphasized by theemphasis circuit depending on whether the image pickup section adopts acomplementary color single CCD, primary color single CCD, double CCD orprimary color triple CCD when applied to a fluorescent mode according toa fourth embodiment of the present invention;

FIG. 15 is a diagram illustrating an example of setting emphasischaracteristics with respect to an emphasized signal emphasized by theemphasis circuit depending on whether the image pickup section adopts acomplementary color single CCD, primary color single CCD, double CCD ortriple CCD when images of fluorescent blue color and red color light arepicked up to generate an observed image;

FIG. 16 is a diagram illustrating an example of setting emphasischaracteristics with respect to an emphasized signal emphasized by theemphasis circuit depending on whether the image pickup section adopts acomplementary color single CCD, primary color single CCD, double CCD ortriple CCD when an image of blue color light is picked up to generate anobserved image;

FIG. 17 is a diagram illustrating an example of setting emphasischaracteristics with respect to an emphasized signal emphasized by theemphasis circuit depending on whether the image pickup section adopts acomplementary color single CCD, primary color single CCD, double CCD ortriple CCD when an image of red color light is picked up to generate anobserved image; and

FIG. 18 is a diagram illustrating an overview of incident light, anemphasized signal emphasized by the emphasis circuit and a signal whoseamount of emphasis is reduced according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, embodiments of the present invention will be described withreference to the accompanying drawings.

First Embodiment

As shown in FIG. 1, an endoscope apparatus 1 according to a firstembodiment is provided with an electronic endoscope (hereinafter, simplyabbreviated to “endoscope”) 2 inserted into a body cavity for performingan endoscope inspection and a light source device 3 that suppliesilluminating light to the endoscope 2. Furthermore, the endoscopeapparatus 1 is also provided with a video processor 4 as an endoscopevideo signal processing apparatus that drives image pickup meansincorporated in the endoscope 2 and performs signal processing on anoutput signal of the image pickup means and a monitor 5 that displays animage obtained by applying signal processing to the pickup imagecaptured by the image pickup means by receiving the video signaloutputted from the video processor 4 as an endoscope image.

The endoscope 2 includes an elongated insertion portion 7, an operationsection 8 provided at a rear end of the insertion portion 7 and auniversal cable 9 that extends from the operation section 8, and a lightguide connector 11 at an end of the universal cable 9 is detachablyconnected to the light source device 3, and a signal connector isdetachably connected to the video processor 4.

A light guide 13 for transmitting illuminating light is inserted intothe insertion portion 7 and illuminating light from the light sourcedevice 3 is supplied to the light guide 13 by connecting the light guideconnector 11 at an end of the operator's hand side in the light guide 13to the light source device 3.

The light source device 3 generates white illuminating light to cover avisible wavelength region as illuminating light and supplies the whiteilluminating light to the light guide 13 in normal white light imaging(abbreviated to “WLI”) mode.

On the other hand, in narrow band imaging (abbreviated to “NBI”) mode,the light source device 3 generates narrow band illuminating light asilluminating light and supplies it to the light guide 13.

Changeover between the WLI mode and NBI mode can be instructed using,for example, a mode changeover switch 14 made up of a scope switchprovided in the operation section 8 of the endoscope 2. The modechangeover switch 14 may be made up of not only the scope switchprovided in the endoscope 2 but also a foot switch, or the modechangeover switch may be provided on the front panel of the videoprocessor 4 or may be made up of a keyboard (not shown).

A changeover signal from the mode changeover switch 14 is inputted to acontrol circuit 15 in the video processor 4 and when the changeoversignal is inputted, the control circuit 15 controls a filterinsertion/removal mechanism 16 of the light source device 3 toselectively switch between normal white light and narrow bandilluminating light.

Furthermore, as will be described later, this control circuit 15 alsoperforms control of changing characteristics of the signal processingsystem in the video processor 4 operating in conjunction with thechangeover control of illuminating light supplied from the light sourcedevice 3 to the light guide 13. Signal processing suitable forrespective observation modes of the WLI mode and NBI mode can beperformed by changing characteristics of the signal processing systemthrough a changeover operation using the mode changeover switch 14.

The light source device 3 incorporates a lamp 20 that generatesilluminating light and the lamp 20 generates illuminating lightincluding a visible wavelength region. With infrared light thereof cutby an infrared cut filter 21, the illuminating light is converted toilluminating light of a wavelength close to a wavelength band ofquasi-white light and then impinged on a diaphragm 22. The aperture ofthe diaphragm 22 is adjusted by a diaphragm drive circuit 23 and thequantity of light passing therethrough is thereby controlled.

The illuminating light that passes through the diaphragm 22 is condensedby a condensing lens 25 after passing through a narrow band filter 24which is inserted/removed into/from an illuminating light path by thefilter insertion/removal mechanism 16 made up of a plunger or the likein the NBI mode or without passing through the narrow band filter 24 inthe WLI mode, and made to impinge on an end face on the operator's handside of the light guide 13, that is, on the incident end face.

FIG. 2 shows an example of spectral characteristics of the narrow bandfilter 24. The narrow band filter 24 shows a two-peak filtercharacteristic and has, for example, narrow band pass filtercharacteristic parts Ga and Ba in wavelength regions of green (G) andblue (B) respectively.

To be more specific, the narrow band pass filter characteristic parts Gaand Ba have center wave lengths of 540 nm and 420 nm respectively andband pass characteristics having a full width at half maximum of 20 to40 nm.

Therefore, when the narrow band filter 24 is placed in the illuminatinglight path, two bands of narrow band illuminating light that have passedthrough the narrow band pass filter characteristic parts Ga and Ba aremade to impinge on the light guide 13.

On the other hand, when the narrow band filter 24 is not placed in theilluminating light path, wide band white light is supplied to the lightguide 13.

The illuminating light from the light guide 13 is transmitted to thedistal end face thereof through the light guide 13, outputted via anillumination lens 27 making up illumination means attached to anilluminating window provided at a distal end portion 26 of the insertionportion 7 and radiated onto, for example, the surface of a living tissuesuch as a diseased part in the body cavity as a subject to irradiate thesurface with illuminating light.

An observation window is provided adjacent to the illuminating window atthe distal end portion 26 and an objective lens 28 is fitted into theobservation window. This objective lens 28 forms an optical image from,for example, reflected light as returning light (or incident light) fromthe living tissue as a subject. One charge coupled device (abbreviatedto “CCD”) 29 as an image pickup device making up image pickup means isplaced at the image forming position of the objective lens 28 and theoptical image is photoelectrically converted by the CCD 29.

For example, a complementary color filter as shown in FIG. 3 is mountedin pixel units on the image pickup surface of the CCD 29 as a colorfilter 30 having a function of a color separation section that performsoptical color separation and color image pickup. That is, the imagepickup section (image pickup device) of the present embodiment is animage pickup device with a complementary color single CCD.

In the complementary color filter, four color chips of magenta (Mg),green (G), cyan (Cy) and yellow (Ye) are arranged in front of eachpixel, Mg and G are alternately arranged in the horizontal direction,and an array of Mg, Cy, Mg, Ye and an array of G, Ye, G, Cy are arrangedsequentially in the vertical direction. In this two-dimensional arraystructure, two pixels in the horizontal direction and four pixels in thevertical direction, a total of eight periodically arrayed pixelsconstitute a (two-dimensional) array structure which is a unit ofperforming color image pickup.

The CCD 29 using the complementary color filter adds up and sequentiallyreads two columns of pixels neighboring each other in the verticaldirection, and reads pixels by shifting the column of pixels between anodd-numbered field and an even-numbered field. From the signal read fromthe CCD 29, a Y/C separation circuit 37 (as first color separationmeans) located after the CCD 29 generates a luminance signal and a colordifference signal, as is publicly known.

An emphasis characteristic is set by an emphasis circuit 48, which willbe described later, according to the unit array structure of the colorfilter 30 in FIG. 3, that is, pixel density per color signal.

The above-described CCD 29 is connected to one end of the signal lineand by connecting a signal connector to which the other end of thesignal line is connected to the video processor 4, the CCD 29 isconnected to a CCD drive circuit 31 and a CDS circuit 32 in the videoprocessor 4.

Each endoscope 2 is provided with an ID generation section 33 thatgenerates identification information (ID) specific to the endoscope 2,the ID from the ID generation section 33 is inputted to the controlcircuit 15 and the control circuit 15 identifies the type of theendoscope 2 connected to the video processor 4, the number and types orthe like of pixels of the CCD 29 incorporated in the endoscope 2 usingthe ID.

The control circuit 15 then controls the CCD drive circuit 31 so as toappropriately drive the CCD 29 of identified endoscope 2.

In the CCD 29, the image pickup signal photoelectrically converted withapplication of the CCD drive signal from the CCD drive circuit 31 isinputted to the correlation double sampling circuit (abbreviated to “CDScircuit”) 32. A signal component is extracted by the CDS circuit 32 froman image pickup signal, converted to a baseband signal, then inputted toan A/D conversion circuit 34 to be converted to a digital signal, andthen inputted to a brightness detection circuit 35 where brightness(average luminance of the signal) is detected.

The brightness signal detected by the brightness detection circuit 35 isinputted to a light adjustment circuit 36 and a light adjustment signalfor adjusting light based on a difference from a reference brightness(light adjustment target value) is generated. The light adjustmentsignal from this light adjustment circuit 36 is inputted to thediaphragm drive circuit 23 and the diaphragm drive circuit 23 adjuststhe aperture of the diaphragm 22 so as to obtain the referencebrightness.

The digital signal outputted from the A/D conversion circuit 34 isinputted to the Y/C separation circuit 37 and the Y/C separation circuit37 generates a luminance signal Y and line sequential color differencesignals Cr′ and Cb′ (as a color signal C in a broad sense). The Y/Cseparation circuit 37 forms first color separation means.

The luminance signal Y is inputted to an expansion circuit 47 via a γcircuit 38 (this luminance signal is represented by Yh) and alsoinputted to a first low pass filter (abbreviated to “LPF”) 41 a whichlimits the passband of the signal.

The LPF 41 a is set to a wide passband in correspondence with theluminance signal Y and a luminance signal Y1 of a band set by thepassband characteristic of this LPF 41 a is inputted to a first matrixcircuit 42.

Furthermore, the color difference signals Cr′ and Cb′ are inputted to a(line sequential) synchronization circuit 43 via a second LPF 41 b thatlimits the passband of the signal.

In this case, the passband characteristic of the second LPF 41 b ismodified by the control circuit 15 according to the observation mode. Tobe more specific, in the WLI mode, the second LPF 41 b is set to a lowerband than the first LPF 41 a. That is, in the WLI mode, a setting ismade so as to perform signal processing (image processing) in conformitywith a typical video signal standard.

On the other hand, in the NBI mode, the second LPF 41 b is modified to awider band than the low band in the WLI mode. For example, the secondLPF 41 b is set (modified) to a wide band in substantially the same wayas the first LPF 41 a.

Thus, the second LPF 41 b forms processing characteristic modifyingmeans for modifying the processing characteristic of limiting thepassband of the color difference signals Cr′ and Cb′ in conjunction withchangeover of the observation mode.

By widening the signal passband characteristic of the second LPF 41 b,it is possible to improve the resolution of the running state of acapillary vessel or the running state of blood vessel close to thesurface layer obtained by a color signal of G, an image of which ispicked up under illuminating light of G close to the luminance signalfrom the narrow band pass filter characteristic part Ga and obtain animage of high image quality, easy to diagnose.

The synchronization circuit 43 generates synchronized color differencesignals Cr′ and Cb′, and the color difference signals Cr′ and Cb′ areinputted to the first matrix circuit 42.

The first matrix circuit 42 converts the luminance signal Y1 and thecolor difference signals Cr′ and Cb′ to three primary color signals R1,G1 and B1. The first matrix circuit 42 outputs the three primary colorsignals R1, G1 and B1 generated to a γ circuit 44 that performs gammacorrection. As described above, although no illuminating light of a redwavelength band is used in the NBI mode, the color signal R1 isequalized to the color signal G1 by a matrix Mat1 shown in [Equation 4]which will be described later.

The (two color signals G1 and B1 of) three primary color signals R1, G1and B1 are also inputted, for example, to the control circuit 15 and asignal intensity ratio calculation circuit 45 in the control circuit 15calculates a signal intensity ratio between the color signals G1 and B1in the NBI mode. The signal intensity ratio calculation circuit 45 isnot necessarily provided inside the control circuit 15, but aconfiguration may be adopted in which the signal intensity ratiocalculation circuit 45 is provided outside the control circuit 15 andthe calculated signal intensity ratio is outputted to the controlcircuit 15.

The signal intensity ratio calculation circuit 45 accumulates signallevels of the color signals G1 and B1 in field or frame units andcalculates signal intensity ratios t and u of the color signals G1 andB1 based on the accumulation result.

The signal intensity ratio calculation circuit 45 may also calculate thesignal intensity ratios t and u by accumulating signal levels within apredetermined region set within an image region, for example, of onefield or one frame.

Assuming the accumulated values of the color signals G1 and B1 withinthe predetermined region are iG and iB respectively, the signalintensity ratios t and u are:t=iG/(iG+iB),u=iB/(iG+iB)  (1)This satisfies a condition of t+u=1. Therefore, the two signal intensityratios t and u may be calculated or one of the two may be calculated andthe remaining one may be calculated from the condition of t+u=1. Thevalues of the signal intensity ratios t and u are reflected in matrixMat3 for matrix calculation by a third matrix circuit 49 which will bedescribed later.

Without being limited to the case of accumulating in field or frameunits to dynamically calculate the signal intensity ratios t and u (thatis, signal intensity ratios t and u dynamically change), the signalintensity ratios t and u may be calculated and values may be fixed tothe calculated values at timing of an initial setting or timinginstructed by a user such as an operator.

The first matrix circuit 42 is controlled by the control circuit 15 andconverts the values of the matrix coefficients (that determineconversion characteristics by the first matrix circuit 42) to themodified three primary color signals R1, G1 and B1 according to thecharacteristics of the color filter 30 of the CCD 29 and thecharacteristics of the narrow band filter 24.

For example, the characteristics of the color filter 30 of the CCD 29mounted in the endoscope 2 may vary depending on the endoscope 2actually connected to the video processor 4 and the control circuit 15changes matrix coefficients to be converted to the three primary colorsignals R1, G1 and B1 by the first matrix circuit 42 according to thetype of the CCD 29 actually used and the spectral characteristics of thecolor filter 30 according to the ID information.

The control circuit 15 incorporates a reference table 15 a to be lookedup to set matrix coefficients by the first matrix circuit 42, the secondmatrix circuit 46 and the third matrix circuit 49, which will bedescribed later.

The γ circuit 44 is also controlled by the control circuit 15. To bemore specific, in the NBI mode, characteristics are modified to γcharacteristics with γ correction characteristics more emphasized thanin the WLI mode. As a result, the contrast on the low signal level sideis emphasized and display characteristics easier to identify areobtained.

The three primary color signals R2, G2 and B2 γ-corrected by the γcircuit 44 are inputted to the second matrix circuit 46 and converted tocolor difference signals R-Y and B-Y by the second matrix circuit 46 asfollows.

$\begin{matrix}\lbrack {{Equation}\mspace{14mu} 1} \rbrack & \; \\{\begin{bmatrix}R \\{R - Y} \\{B - Y}\end{bmatrix} = {{Mat}\;{2 \cdot \begin{bmatrix}{R\; 2} \\{G\; 2} \\{B\; 2}\end{bmatrix}}}} & \;\end{matrix}$

Matrix Mat2 is expressed as shown in Equation (2b).

For example, matrix coefficients of fixed values (common set values) areadopted for the second matrix circuit 46 irrespective of whether theobservation mode is changed to the WLI mode or NBI mode.

The color difference signals R-Y and B-Y outputted from the secondmatrix circuit 46, together with the luminance signal Yh gamma-correctedby the γ circuit 38, are inputted to the expansion circuit 47 thatperforms expansion processing.

The luminance signal Yh (hereinafter described as “Y” for simplicity)and the color difference signals R-Y and B-Y are subjected to expansionprocessing by the expansion circuit 47 and then inputted to the emphasiscircuit 48 as emphasis processing means for performing sharpnessemphasis processing. The expansion circuit 47 and the emphasis circuit48 are provided in a 3-circuit configuration in correspondence with theluminance signal Y and the two color difference signals R-Y and B-Y.

The emphasis circuit 48 emphasizes the sharpness of contours orstructure of a mucous membrane image reproduced to an image signal andoutputs the emphasized luminance signal Y and color difference signalsR-Y and B-Y to the third matrix circuit 49 as second color separationmeans.

The expansion processing by the expansion circuit 47 and the emphasisprocessing by the emphasis circuit 48 are controlled by the controlcircuit 15 as control means.

Furthermore, the control circuit 15 has a table 15 b as storing meansfor storing the type (class) of the CCD 29 as image pickup means andinformation for modifying (changing) processing contents of the emphasiscircuit 48 according to spectral characteristics of light (incident onthe CCD 29) which vary depending on the observation mode.

The table 15 b as the above-described storing means may also be providedoutside the control circuit 15. Furthermore, the table 15 b may also beprovided inside the emphasis circuit 48.

The control circuit 15 forms control means for performing control ofreading the type of the CCD 29 and the information corresponding to theobservation mode from the table 15 b and automatically modifyingprocessing contents of the emphasis circuit 48 according to theinformation.

The control circuit 15 recognizes the type of the CCD 29 using the IDfrom the ID generation section 33. Furthermore, the control circuit 15recognizes the observation mode through a changeover operation of themode changeover switch 14. The control circuit 15 performs control ofautomatically modifying the processing contents of the emphasis circuit48 to different processing contents in the WLI mode and NBI modeaccording to the observation mode based on the type of the CCD 29 andthe observation mode.

Furthermore, according to a manual instruction by the user such asoperator from a setting section 50 provided in the video processor 4,the control circuit 15 may also be adapted to be able to modify theamount of emphasis of the sharpness in response to the instruction.

The third matrix circuit 49 converts the inputted luminance signal Y andcolor difference signals R-Y and B-Y to three primary color signals R, Gand B. The three primary color signals R, G and B generated by the thirdmatrix circuit 49 are converted to analog video signals by a D/Aconversion circuit (not shown) and outputted from a video signaloutputted end to the monitor 5.

The third matrix circuit 49 is set in such a way that the matrix Mat3becomes an inverse matrix of matrix Mat2 of the second matrix circuit 46in the WLI mode.

To be more specific, when the matrix composed of matrix elements ofthree rows and three columns of the second matrix circuit 46 is assumedto be Mat2, if Mat2 ⁻¹ is expressed by an inverse matrix of matrix Mat2,matrix Mat3 in the WLI mode is set as:Mat3=Mat2⁻¹  (2a)

Regarding this matrix Mat2, as a matrix for converting RGB signals to Ycolor difference signal, the following publicly known calculationcoefficient or the like are used.

$\begin{matrix}\lbrack {{Equation}\mspace{14mu} 2} \rbrack & \; \\{{{Mat}\; 2} = \begin{bmatrix}0.299 & 0.587 & 0.114 \\0.701 & {- 0.587} & {- 0.114} \\{- 0.299} & {- 0.587} & 0.886\end{bmatrix}} & ( {2b} )\end{matrix}$

On the other hand, in the NBI mode, when a matrix resulting fromsubstituting 0, t and u for the matrix elements on the first row ofabove-described matrix Mat2 is represented by Mat2′ and if

$\begin{matrix}\lbrack {{Equation}\mspace{14mu} 3} \rbrack & \; \\{{{Mat}\; 2^{\prime}} = \begin{bmatrix}0 & t & u \\0.701 & {- 0.587} & {- 0.114} \\{- 0.299} & {- 0.587} & 0.886\end{bmatrix}} & \;\end{matrix}$

-   -   is assumed, the third matrix circuit 49 is set in such a way        that matrix Mat3 thereof becomes an inverse matrix of matrix        Mat2′ of the second matrix circuit 46.

When Mat2′⁻¹ is expressed by an inverse matrix of matrix Mat2′, matrixMat3 in the NBI mode is set as:Mat3=Mat2′⁻¹  (2c)

In the NBI mode, the first matrix circuit 42 is set to matrix Mat1 madeup of matrix elements m21, . . . , m33 as shown in Equation (3) below.Matrix elements m21, m22 and m23 on the first row become the same matrixelements on the second row, and the conversion output of the first rowis the same as that of the second row.

$\begin{matrix}\lbrack {{Equation}\mspace{14mu} 4} \rbrack & \; \\{{{Mat}\; 1} = \begin{bmatrix}{m\; 21} & {m\; 22} & {m\; 23} \\{m\; 21} & {m\; 22} & {m\; 23} \\{m\; 31} & {m\; 32} & {m\; 33}\end{bmatrix}} & (3)\end{matrix}$

Furthermore, in the present embodiment, for example, a display colorconversion setting section 50 a is provided in the setting section 50that makes settings for converting and displaying display colors so thatan endoscope image may be displayed in colors in the NBI mode to beeasily visually recognizable to the operator.

When the display color conversion function in the display colorconversion setting section 50 a is turned ON, the control circuit 15performs control so as to use matrix Mat3 obtained by multiplying theinverse matrix of above-described matrix Mat2′ by matrix Mat_(NBI-C-Tf)that converts display colors.

In this case, matrix Mat3 is set as:Mat3=Mat_(NBI-C-Tf′)Mat2′⁻¹  (4)

Here, when a matrix having matrix elements k1, k2 and k3 is assumed tobe K, Mat_(NBI-C-Tf) is expressed by:

$\begin{matrix}\lbrack {{Equation}\mspace{14mu} 5} \rbrack & \; \\\begin{matrix}{{Mat}_{{NBI}\text{-}C\text{-}{Tf}} = K} \\{= \begin{bmatrix}0 & {k\; 1} & 0 \\0 & 0 & {k\; 2} \\0 & 0 & {k\; 3}\end{bmatrix}}\end{matrix} & (5)\end{matrix}$

When converting display colors by operating the display color conversionsetting section 50 a, the operator may be allowed to variably set thevalues of color conversion matrix elements k1, k2 and k3.

As described above, the present embodiment changes processing contentson emphasized signals as the image signals subjected to emphasisprocessing by the emphasis circuit 48 according to the observation mode.To be more specific, in the WLI mode, the emphasis circuit 48 performsemphasis processing of adding a result of convolutional calculationusing digital filters (DC component=0) in a predetermined filter size toinput signals (luminance signal Y and two color difference signals R-Yand B-Y) to the emphasis circuit 48 on the luminance signal Y and twocolor difference signals R-Y and B-Y.

For this purpose, the table 15 b stores filter coefficients of thedigital filters for performing emphasis processing by the emphasiscircuit 48 for the WLI mode and for the NBI mode.

According to a unit array structure of a plurality of filter elementsmaking up the color filter 30 as the aforementioned color separationsection, a pixel density for generating the luminance signal Yh isgreater than the pixel density for generating the color differencesignals Cr′ and Cb′, and therefore filter coefficients are set asfollows according to the array structure corresponding to the pixeldensity. That is, filter coefficients are set so as to have an emphasischaracteristic having a greater amount of emphasis for an image signalwith a high pixel density than for an image signal with a low pixeldensity. In other embodiments which will be described later, filtercoefficients are also set according to the array structure basicallycorresponding to the pixel density of the color separation section.

Filter coefficient WLI-Y for a luminance signal, filter coefficientWLI-R-Y (that is, WLI-Cr) for a color difference signal R-Y and filtercoefficient WLI-B-Y (WLI-Cb) for a color difference signal B-Y arestored as emphasis processing filter coefficients for the WLI mode. Forthe filter coefficients WLI-Cr and WLI-Cb for color difference signals,values obtained by multiplying all filter coefficients of the filtercoefficient WLI-Y for a luminance signal by a constant ka (ka<1) arestored.

On the other hand, as emphasis processing filter coefficients for theNBI mode, filter coefficient NBI-Y for a luminance signal, filtercoefficient NBI-R-Y (that is, NBI-Cr) for a color difference signal R-Yand filter coefficient NBI-B-Y (NBI-Cb) for a color difference signalare stored, and values equal to the filter coefficient WLI-Y for aluminance signal are stored for the filter coefficient NBI-Y for aluminance signal, filter coefficients of all zeros are stored for thefilter coefficient NBI-Cr for a color difference signal, and valuesobtained by multiplying all filter coefficients of filter coefficientNB1-Y for a luminance signal by constant kb (kb<1) are stored for thefilter coefficient NBI-Cb for a color difference signal.

Furthermore, in this case, constants ka and kb are set so as to beka<kb, that is, the amount of emphasis for the color difference signalCb in the NBI mode is greater (stronger) than that in the WLI mode.

Therefore, an overview of an emphasis characteristic example whenemphasis processing is performed by the emphasis circuit 48 using theabove-described emphasis processing coefficients in the WLI mode and theNBI mode is as shown in FIG. 4. As shown in FIG. 4, a greater amount ofemphasis is set for the luminance signal Y shown by a solid line thanthe color difference signals Cr, Cb shown by a dotted line over theentire frequency domain.

In the case of NBI, the amount of emphasis is set so as to havesubstantially the same tendency for the luminance signal Y and one colordifference signal Cb. However, a relative emphasis characteristic of thecolor difference signal Cb with respect to the luminance signal Y is setto a characteristic that the amount of emphasis is greater than that inthe WLI mode as described above. This situation is shown by a two-dotdashed line in FIG. 4.

The emphasis processing by the emphasis circuit 48 may also be adaptedso that the emphasis characteristic thereof can be modified according tothe type of the CCD 29 and color filter 30 or the like via the controlcircuit 15 according to an operation from the emphasis setting sectionin the setting section 50.

The endoscope apparatus 1 in the present embodiment in such aconfiguration includes the CCD 29 as image pickup means provided withthe color filter 30 as a color separation section that color-separates,receives and picks up an image of returning light of light radiated ontoa subject by illumination means and the emphasis circuit 48 as emphasisprocessing means for performing sharpness emphasis processing on animage signal based on the image pickup means.

Furthermore, the endoscope apparatus 1 includes the table 15 b asstoring means for storing information for modifying processing contentsof the emphasis processing means according to the spectralcharacteristics of the returning light incident on the image pickupmeans which differ depending on the type of the image pickup means andobservation mode, and the control circuit 15 as control means forperforming control of modifying processing contents of the emphasisprocessing means based on the information of the storing means.

Next, main operations of the present embodiment will be described belowwith reference to FIG. 5.

When the operator connects the endoscope 2 to the light source device 3and the video processor 4 as shown in FIG. 1 and turns on the power, thecontrol circuit 15 of the video processor 4 starts initial setupprocessing. As shown in step S1, the control circuit 15 causes the lightsource device 3 and the video processor 4 to be set, for example, in anoperating mode corresponding to the observation mode of the WLI mode.The control circuit 15 may also cause the light source device 3 and thevideo processor 4 to be set in an observation mode instructed by theoperator.

When the WLI mode is set, the light source device 3 is set in a state inwhich the narrow band filter 24 is separated from the illuminating lightpath as shown by a solid line in FIG. 1 and the endoscope 2 is set toperform image pickup under white illuminating light. Furthermore, thesections on the video processor 4 side are also set to perform signalprocessing in the WLI mode.

As shown in step S2, the control circuit 15 identifies, using the IDfrom the ID generation section 33, the type of the image pickup means,that is, identifies that the type of the CCD 29 is a single CCD and thecolor filter 30 of the CCD 29 is a single CCD complementary colorfilter.

Then, as shown in step S3, with reference to the table 15 b usinginformation on the observation mode and the type of the CCD 29, thecontrol circuit 15 sets filter coefficients used when performingemphasis processing through the emphasis circuit 48, that is, sets anemphasis characteristic.

The emphasis circuit 48 whose filter coefficients are set in this wayhas an emphasis characteristic as shown in FIG. 4. As shown in FIG. 4,the luminance signal is set to have a greater amount of emphasis thanthe color difference signal. With such a setting, when sharpness isemphasized so that edges of a living tissue or the like becomes clearer,since the emphasis characteristic corresponding to a pixel density isset, it is possible to lay emphasis while suppressing the occurrence offalse color or color moire.

Furthermore, as shown in step S4, with reference to the table 15 a, thecontrol circuit 15 sets matrix coefficients for performing matrixcalculations using the first matrix circuit 42, the second matrixcircuit 46 and the third matrix circuit 49 respectively.

As shown in step S5, the video processor 4 performs image processingusing the above-described filter coefficients and matrix coefficients,generates three primary color signals R, G and B as image signals of anendoscope image via the third matrix circuit 49 and outputs them to themonitor 5. The monitor 5 displays the endoscope image as an observedimage corresponding to the image signals. The operator performs anendoscope inspection of a tissue to be examined such as diseased part inthe body cavity while observing this endoscope image.

In next step S6, the control circuit 15 monitors whether or not a modechangeover operation has been carried out. When the mode changeoveroperation has not been carried out, the process returns to step S5 andthe process of displaying the endoscope image in the WLI mode continues.

When attempting to observe the running state or the like of a bloodvessel on the surface of the tissue to be examined in detail, theoperator operates the mode changeover switch 14.

When the mode changeover switch 14 is operated, the control circuit 15modifies the observation mode of the light source device 3 and videoprocessor 4 to the NBI mode as shown in step S7.

To be more specific, the control circuit 15 controls the light sourcedevice 3 so as to place the narrow band filter 24 in the illuminatinglight path as shown by a two-dot dashed line in FIG. 1. When the narrowband filter 24 is placed in the illuminating light path, whosetransmission characteristic is shown in FIG. 2, illumination isperformed using narrow band illuminating light with narrow band passfilter characteristic parts Ga and Ba.

Furthermore, the control circuit 15 modifies settings of the sections ofthe video processor 4. To be more specific, the control circuit 15widens the band characteristic of the LPF 41 b.

Furthermore, the control circuit 15 widens the signal passbandcharacteristic of the LPF 41 b and improves the resolution of therunning state of the capillary vessel and the blood vessel running stateor the like close to the surface layer obtained by the color signal ofG, an image of which is picked up under illuminating light of G close tothe luminance signal by the narrow band pass filter characteristic partGa as described above.

Furthermore, in next step S8, the control circuit 15 refers to the table15 b as the mode is changed to the NBI mode and sets a filtercoefficient used when performing emphasis processing through theemphasis circuit 48, that is, sets the emphasis characteristic.

The emphasis circuit 48 whose filter coefficient is set in this way hasan emphasis characteristic as shown in FIG. 4. The amount of emphasis ofthe luminance signal Y is set to be greater than that of the colordifference signal Cb in both the NBI mode and WLI mode. As in the caseof the WLI mode, such a setting makes it possible to place emphasiswhile suppressing the occurrence of false color or color moire.Moreover, since the amount of emphasis of the color difference signal isset to be greater than in the WLI mode, it is easier to identifycontours and edges or the like of a blood vessel.

Furthermore, in step S9, the signal intensity ratio calculation circuit45 calculates a signal intensity ratio t. The control circuit 15 setsmatrix coefficients for performing matrix calculations using the firstmatrix circuit 42, the second matrix circuit 46 and the third matrixcircuit 49 with reference to the values of the calculated signalintensity ratio t and the table 15 a.

As shown in step S10, the video processor 4 performs image processingusing the above-described filter coefficients and matrix coefficients,generates three primary color signals R, G and B as image signals of theendoscope image through the third matrix circuit 49 and outputs thethree primary color signals R, G and B to the monitor 5. The monitor 5displays the endoscope image as an observed image corresponding to theimage signals.

When the display color conversion setting section 50 a is OFF, the thirdmatrix circuit 49 generates color signals R, G and B as three primarycolor signals not to be subjected to display color conversion, and whenthe display color conversion setting section 50 is ON, the third matrixcircuit 49 generates three primary color signals R, G and B subjected todisplay color conversion.

The operator performs an endoscope inspection while observing thisendoscope image in a condition in which the running state of thecapillary vessel or the like close to the surface of a tissue to beexamined in the body cavity can be easily identified in more detail.

In next step S11, the control circuit 15 monitors whether or not a modechangeover operation has been performed. When the mode changeoveroperation has not been performed, the process returns to step S10 andcontinues the process of displaying the endoscope image in the NBI mode.

On the other hand, when the mode changeover operation has beenperformed, the process returns to step S1.

According to the present embodiment that operates in this way, theemphasis circuit 48 can perform emphasis processing while suppressingthe occurrence of false color or color moire. Therefore, the presentembodiment can provide an endoscope image as an observed image of highquality, allowing the operator to easily make a diagnosis or the like.

Furthermore, since the present embodiment adopts a high frequency bandfor the signal band of the color difference signal also in the NBI mode,it is possible to obtain a high resolution endoscope image and displaythe running state of the capillary vessel or the like in a more clearlyand easily identifiable condition.

Furthermore, the present embodiment adopts a configuration of generatingan image signal through matrix calculation in the third matrix circuit49 according to the signal intensity ratios t and u of the color signalsG1 and B1 in the NBI mode, and can thereby convert a luminance signal toa color signal according to the signal intensities of the color signalsG1 and B1 and prevent deterioration of the contrast of the endoscopeimage in the NBI mode.

Furthermore, the present embodiment can easily support both the WLI modeand NBI mode by changing part of processing characteristics in thesignal processing system (image processing system), and can therebyprovide a highly convenient and useful apparatus during an endoscopeinspection.

Furthermore, by providing means for inserting/removing the narrow bandfilter 24 in/from the optical path in addition to illumination means ofnormal white light, the light source device 3 can also easily form alight source device of narrow band light.

In the aforementioned first embodiment, the emphasis characteristic ofthe emphasis circuit 48 is set as shown in FIG. 4, but an emphasischaracteristic as shown in FIG. 6 may also be set as a modificationexample of the emphasis characteristic.

As for the luminance signal Y, the emphasis characteristic shown in FIG.6 is set to an emphasis characteristic similar to that shown in FIG. 4in both the WLI mode and the NBI mode, while as for the color differencesignals Cr and Cb (in WLI mode) or Cb (in NBI mode), filter coefficientsare set so as to have frequency characteristics in which the amount ofemphasis is smaller on the high frequency band side having a higherfrequency.

Adopting such a frequency characteristic makes it possible to reduce theoccurrence of color moire which becomes conspicuous on the highfrequency band side.

As a modification example, it may be possible to designate only theluminance signal Y as an emphasized signal and emphasize only theluminance signal Y through the emphasis circuit 48 in the WLI mode,while in the NBI mode, it may be possible to designate the luminancesignal Y and the color difference signal Cb as emphasized signals andemphasize the luminance signal Y and the color difference signal Cbthrough the emphasis circuit 48.

Furthermore, as another modification example, it may be possible toadopt three-peak spectral characteristics for the narrow band filter,further have a narrow band pass filter characteristic part Ra (centerwave length of 600 nm and full width at half maximum of 20 to 40 nm) anddesignate the luminance signal Y and the color difference signals Cb(B-Y) and Cr (R-Y) as emphasized signals in the NBI mode, and performemphasis processing on the luminance signal Y and the color differencesignals Cb and Cr through the emphasis circuit 48 so that the emphasischaracteristic is weaker with the color difference signals Cb and Crthan the luminance signal Y and the same between the color differencesignals Cb and Cr.

First Modification Example of First Embodiment

FIG. 7 shows an overall configuration of an endoscope apparatus 1Baccording to a first modification example of the first embodiment of thepresent invention. The present modification example has a configurationin which a fourth matrix circuit 51 is provided before the emphasiscircuit 48 in the video processor 4 in the first embodiment shown inFIG. 1.

The fourth matrix circuit 51 performs a matrix calculation of generatingemphasized signals Y, Cr and Cb having a high color moire reductioneffect on the luminance signal Y and color difference signals R-Y andB-Y outputted from the expansion circuit 47 and inputted to the fourthmatrix circuit 51 using matrix Mat4.

That is, when emphasized signals which are signals inputted to theemphasis circuit 48 are represented by Y, Cr and Cb as described above,the fourth matrix circuit 51 converts them as shown in Equation (6) andadopts matrix Mat4 as shown in Equations (7) and (8) in the WLI mode andthe NBI mode respectively.

$\begin{matrix}\lbrack {{Equation}\mspace{14mu} 6} \rbrack & \; \\{\begin{bmatrix}Y \\{Cr} \\{Cb}\end{bmatrix} = {{Mat}\;{4 \cdot \begin{bmatrix}Y \\{R - Y} \\{B - Y}\end{bmatrix}}}} & (6) \\{{{Mat}\; 4} = {\begin{bmatrix}1 & 0 & 0 \\0 & a & 0 \\0 & 0 & b\end{bmatrix}( {{WLI}\mspace{14mu}{mode}} )}} & (7) \\{{{Mat}\; 4} = {\begin{bmatrix}1 & 0 & 0 \\0 & 0 & 0 \\0 & 0 & c\end{bmatrix}( {{NBI}\mspace{14mu}{mode}} )}} & (8)\end{matrix}$where, a, b, c≦1

Matrix Mat3 by the third matrix circuit 49 in the present embodiment isset to:Mat3=Mat2⁻¹  (9)in the same way as in the first embodiment in the WLI mode. On the otherhand, unlike the first embodiment, matrix Mat3 in the NBI mode is setto:Mat3=Mat_(NBI-C-Tf′)Mat41NBI⁻¹  (10)Here, matrix Mat41 _(NBI) is expressed by:

$\begin{matrix}\lbrack {{Equation}\mspace{14mu} 11} \rbrack & \; \\{{{Mat}\; 41_{NBI}} = \begin{bmatrix}{m\; 11} & {m\; 12} & {m\; 13} \\0.701 & {- 0.587} & {- 0.114} \\{- 0.299} & {- 0.587} & 0.886\end{bmatrix}} & (11)\end{matrix}$

Matrix elements m11, m12 and m13 are predetermined values. The matrixelements m11, m12 and m13 are set based on signal intensity ratiosbetween R, G and B in the luminance signal Yh. Alternatively, m12=t,m13=u and m11=0 are set using the signal intensity ratios t and ucalculated by the aforementioned signal intensity ratio calculationcircuit 45.

The rest of the configuration is similar to that of the firstembodiment. The present modification example generates an emphasizedsignal having a high color moire reducing effect and performs emphasisprocessing through the emphasis circuit 48, and can thereby reduce colormoire more than the first embodiment. In other aspects, the presentmodification example has operations and effects similar to those of thefirst embodiment.

When the fourth matrix circuit 51 performs conversion as shown inEquation (6), the conversion may be performed as shown in the followingsecond modification example.

In the second modification example, in the NBI mode, Mat4 may beexpressed by the following equation instead of Equation (8):Mat4=Mat42_(NBI′)Mat41_(NBI) ⁻¹  (12)where, Mat42 _(NBI) is expressed by:

$\begin{matrix}\lbrack {{Equation}\mspace{14mu} 13} \rbrack & \; \\{{{Mat}\; 42_{NBI}} = \begin{bmatrix}{m\; 11} & {m\; 12} & {m\; 13} \\0 & 0 & 0 \\{m\; 31} & {m\; 32} & {m\; 33}\end{bmatrix}} & (13)\end{matrix}$where the matrix elements m31, m32 and m33 are predetermined values. Thematrix elements m31, m32 and m33 are values that satisfym11*m31+m12*m32+m13*m33=0. Mat41 _(NBI) is expressed by Equation (11).

Furthermore, in this case, as in the case of the first embodiment,matrix Mat3 of the third matrix circuit 49 in the WLI mode is set to:Mat3=Mat2⁻¹  (14)On the other hand, unlike the first embodiment, Mat3 in the NBI mode isset as:Mat3=Mat_(NBI-C-Tf′)Mat42_(NBI) ⁻¹  (15)Matrix Mat_(NBI-C-Tf) is expressed by Equation (5). Matrix Mat42 _(NBI)⁻¹ is not limited to the case with an inverse matrix of Mat42 _(NBI)expressed by Equation (13).

For example, suppose a pseudo-inverse matrix (3 rows, 2 columns) of amatrix (2 rows, 3 columns) composed of the first and third row elementsof matrix Mat42 _(NBI) may be derived and a matrix of 3 rows and 3columns (all elements of the second column are 0) whose first and secondcolumn elements are designated as their respective first and thirdcolumn elements may be used. This second modification example hasoperations and effects substantially the same as those of the firstmodification example.

Second Embodiment

FIG. 8 shows an overall configuration of an endoscope apparatus 1Caccording to a second embodiment of the present invention. The endoscopeapparatus 1C is made up of an endoscope 2C, a light source device 3, avideo processor 4C and a monitor 5.

For the endoscope 2C, for example, an image pickup device with a primarycolor single CCD is adopted instead of the image pickup device withcomplementary color single CCD in the endoscope 2 in FIG. 1. That is, acolor filter 30 c with a primary color single CCD Bayer array as shownin FIG. 9 is adopted for the image pickup surface of the CCD 29.

This color filter 30 c has a filter array in which a unit of four filterelements of two rows and two columns in the horizontal and verticaldirections is periodically arranged in the horizontal and verticaldirections. In this case, color filter elements of R, G and G, B arealternately arranged in the horizontal and vertical directions.

The CCD 29 is driven by the CCD drive circuit 31 in the same way as, forexample, in the first embodiment. The video processor 4C in this casehas a configuration in which the output signal of the A/D conversioncircuit 34 in the video processor 4 in FIG. 1 is inputted to the LPF 52via a changeover circuit (not shown) that switches between outputsignals in pixel units.

By passing through the LPF 52, missing pixel values of color signals ateach pixel position are calculated, and synchronized three primary colorsignals R, G and B are generated. The three primary color signals R, Gand B generated after passing through the LPF 52 are subjected to whitebalance processing through a white balance circuit (abbreviated to “WBcircuit”) 53 and then inputted to a γ circuit 54 that performs gammacorrection.

The three primary color signals R, G and B outputted from the γ circuit54 are inputted to an expansion circuit 47 as in the case of theconfiguration of the video processor 4 in FIG. 1, subjected to expansionprocessing and inputted to an emphasis circuit 48 that performssharpness emphasis processing on the three signals.

After being subjected to emphasis processing through the emphasiscircuit 48, the three signals are generated into three primary colorsignals R, G and B by a third matrix circuit 49 as an image signal ofthe endoscope image as an observed image and outputted to the monitor 5.

According to the present embodiment, in the WLI mode, the emphasizedsignals are three primary color signals R, G and B and the emphasiscircuit 48 performs emphasis processing on the three primary colorsignals R, G and B as the emphasized signals. As for the amount ofemphasis in this case, WLI filter coefficients are stored in a table 15b so that the amount of emphasis on G becomes greater than the amountsof emphasis on other R and B.

On the other hand, in the NBI mode, the emphasized signals are (twocolor signals in) three primary color signals G and B, and the emphasiscircuit 48 performs emphasis processing on the (color signals as)emphasized signals G and B. As for the amount of emphasis in this case,NBI filter coefficients are stored in the table 15 b so that the amountof emphasis on G is greater than the amount of emphasis on other B.

That is, the table 15 b stores WLI-RB filter coefficients and WLI-Gfilter coefficients as WLI filter coefficients, and stores NBI-B filtercoefficients and NBI-G filter coefficients as NBI filter coefficients.

The WLI-RB filter coefficients and the NBI-B filter coefficients are setto values obtained by multiplying all the WLI-G filter coefficients andNBI-G filter coefficients by constant ka (ka<1).

The present embodiment sets common constant ka in the WLI mode and NBImode, but constants ka and kb may be set in the WLI mode and NBI mode soas to be ka<kb as in the first embodiment.

Furthermore, in the present embodiment, the third matrix circuit 49performs matrix calculation using a unit matrix in the WLI mode. On theother hand, the third matrix circuit 49 performs matrix calculationusing matrix Mat_(NBI-C-Tf) shown in aforementioned Equation (5) in theNBI mode. That is, when input/output signals RGB to/from the thirdmatrix circuit 49 are assumed to be Rin, Gin, Bin, Rout, Gout and Bout,the third matrix circuit 49 performs the following matrix calculation.

$\begin{matrix}\lbrack {{Equation}\mspace{14mu} 16} \rbrack & \; \\{\begin{bmatrix}{Rout} \\{Gout} \\{Bout}\end{bmatrix} = {{Mat}_{{NBI}\text{-}C\text{-}{Tf}} \cdot \begin{bmatrix}{Rin} \\{Gin} \\{Bin}\end{bmatrix}}} & \;\end{matrix}$

The table 15 a stores matrix coefficients used in the third matrixcircuit 49.

Operation of the present embodiment in such a configuration is differentin the emphasized signals from the first embodiment, but the basicoperation thereof is similar to that of the first embodiment.

Since the emphasis circuit 48 of the present embodiment is also set toan emphasis characteristic corresponding to the pixel density, theemphasis circuit 48 can perform emphasis processing while suppressingthe occurrence of false color or color moire. Therefore, according tothe present embodiment, it is possible to provide an endoscope image asan observed image of high quality allowing the operator to easily make adiagnosis or the like.

Furthermore, the present embodiment does not apply band limitation evenin the NBI mode, and can thereby obtain an endoscope image of highresolution and display the running state of a capillary vessel or thelike in a more clearly and easily identifiable condition.

Furthermore, the present embodiment can easily support both the WLI modeand NBI mode by changing part of processing characteristics in thesignal processing system, and can thereby provide a highly convenientand useful apparatus during an endoscope inspection.

A case of an image pickup device with a primary color single CCD hasbeen described in the present embodiment, but an image pickup devicewith a primary color double CCD, that is, an image pickup section madeup of two image pickup devices may also be adopted.

FIG. 10 shows a configuration of a periphery of the image pickup sectionat a distal end portion 26 of an endoscope 2C′ in this case. A first CCD29 a is arranged at an image forming position on the optical axis of anobjective lens 28. A half mirror 56 which passes and reflectssubstantially 50% of incident light is placed at some midpoint on theoptical axis.

A second CCD 29 b is placed at an image forming position on the opticalaxis of light reflected by the half mirror 56. Color filters 30 a and 30b with primary colors as shown in FIG. 11 are arranged on the imagepickup surfaces of the first CCD 29 a and the second CCD 29 b as colorseparation sections.

The color filter 30 a is made up of only Gs as filter elements. On theother hand, the color filter 30 b is made up of Rs and Bs as filterelements.

A unit array structure for generating color signals for performing colorimage pickup using both the color filters 30 a and 30 b corresponds topixels of two rows and two columns and color signals generated from unitpixels are 4Gs+2(R+B)s. In the case of the color filter 30 c in FIG. 9,color signals generated from pixels of two rows and two columnscorresponding to the unit array for generating color signals are2Gs+R+B. The first CCD 29 a and the second CCD 29 b are driven by acommon CCD drive circuit 31. Furthermore, the output signals of thefirst CCD 29 a and second CCD 29 b are converted to baseband signalcomponents by CDS circuits 32 a and 32 b respectively.

The output signals of the CDS circuits 32 a and 32 b are subjected togain adjustment for correcting characteristics of the half mirror 56 byan amplifier (not shown), and then added up by an adder 57 and inputtedto the A/D conversion circuit 34 shown in FIG. 8.

The signal inputted to the A/D conversion circuit 34 is a signal atresolution twice as high as that in the case of FIG. 8. The processingafter the A/D conversion circuit 34 is the same as that in FIG. 8.

According to the present modification example, it is possible togenerate an endoscope image with higher resolution. Other operations andeffects are the same as those of the second embodiment.

Furthermore, as a modification example of the above-described secondembodiment and a modification example of the modification example,filter coefficients may be set such that the amount of emphasis of thecolor signal G is greater than those of the color signal R and B (in WLImode) or B (in NBI mode) only on the high frequency side instead ofmaking the amount of emphasis of the color signal G greater than thoseof the color signals R and B (in WLI mode) or B (in NBI mode).

Furthermore, in the embodiment shown in FIG. 8, the emphasis circuit 48is configured to perform emphasis processing on the color signals R, Gand B (in WLI mode) or G and B (in NBI mode), but a configuration mayalso be adopted in which those signals are converted to a luminancesignal Y and color difference signals Cr and Cb and the emphasis circuit48 performs emphasis processing on the converted luminance signal Y andcolor difference signals Cr and Cb.

Third Embodiment

FIG. 12 shows an overall configuration of an endoscope apparatus 1Daccording to a third embodiment of the present invention. This endoscopeapparatus 1D is made up of an endoscope 2D, a light source device 3, avideo processor 4D and a monitor 5. The endoscope 2D is mounted with animage pickup section made up of an image pickup device with a primarycolor triple CCD instead of the (image pickup section made up of) oneimage pickup device placed at the distal end portion 26 of the insertionportion 7 in the endoscope 2 in FIG. 1.

Color separation prisms 61 a, 61 b and 61 c as a color separationsection to perform color separation into R, G and B and three CCDs 29R,29G and 29B arranged at their respective image forming positions areprovided on the optical axis of the objective lens 28. Therefore, inthis case, the three CCDs 29R, 29G and 29B each output R, G and B colorsignals in pixel units. The present embodiment corresponds to a unitarray in the case where one pixel performs color image pickup.

Therefore, in the case of the present embodiment, as shown in FIG. 13,signals color-separated into R, G and B in pixel units are outputted.Without being limited to the configuration example of the image pickupdevice with a primary color triple CCD having the structure shown inFIG. 12, a triple CCD image pickup device in which color-separatingprimary color filters as shown in FIG. 13 are attached to image pickupsurfaces of three CCDs may also be used.

The above-described CCDs 29R, 29G and 29B are driven by a common CCDdrive circuit 31.

Furthermore, output signals of the CCD 29R, 29G and 29B are inputted toa three-line CDS circuit 32′ and baseband color signals R, G and B areoutputted from this CDS circuit 32′ to a three-line A/D conversioncircuit 34′ and a brightness detection circuit 35.

The digital color signals R, G and B, which are A/D-converted by the A/Dconversion circuit 34′, are inputted to an RGB-Y/C separation circuit 62and converted to a luminance signal Y and color difference signals Crand Cb.

The processing configuration corresponding to the luminance signal Y andcolor difference signals Cr and Cb as the output signals from theRGB-Y/C separation circuit 62 and the rest is similar to theconfiguration example shown in FIG. 1. However, as shown below, theemphasis characteristic of the emphasis circuit 48 is different fromthat in FIG. 1.

A table 15 b stores filter coefficients for emphasis processing by theemphasis circuit 48 in the present embodiment, too.

In the present embodiment, WLI-Y/Cr/Cb filter coefficients and NBI-Y/Cbfilter coefficients are stored as filter coefficients for emphasisprocessing and to be stored in the table 15 b, and the same values arestored as all the WLI-Y/Cr/Cb filter coefficients and NBI-Y/Cb filtercoefficients (NBI-Cr filter coefficients are zero). Since the pixeldensity, that is, the pixel density when color signals R, G and B aregenerated is the same, the present embodiment is also set so as to haveemphasis characteristics corresponding to the same value.

The control circuit 15 sets filter coefficients for emphasis processingby the emphasis circuit 48 with reference to the table 15 b for eachobservation mode.

Furthermore, the table 15 a stores matrix coefficients of the firstmatrix circuit 42, the second matrix circuit 46 and the third matrixcircuit 49 as in the case of the first embodiment. Matrix calculationssimilar to those in the first embodiment are performed.

Operation in the present embodiment is similar to the operation of theimage pickup section made up of a single CCD image pickup deviceprovided with a complementary color filter of the first embodimentsubstituted by an image pickup section made up of an image pickup devicewith a primary color triple CCD.

However, unlike the first embodiment, the present embodiment performsemphasis processing with the same emphasis characteristic on theluminance signal Y and the color difference signals Cr and Cb incorrespondence with the image pickup device with a primary color tripleCCD.

Performing emphasis processing corresponding to the image pickup devicewith a primary color triple CCD in this way makes it possible to improvereproducibility of a blood vessel image through emphasis processing.Furthermore, use of the image pickup device with a primary color tripleCCD makes it possible to obtain an endoscope image with higherresolution than that in the first embodiment.

As a modification example of the present embodiment, a configuration maybe adopted in which the output signal of the A/D conversion circuit 34′in FIG. 12 is outputted to the WB circuit 53 in FIG. 8.

In that case, WLI-RGB filter coefficients and NBI-GB filter coefficientsare stored as filter coefficients for emphasis processing to be storedin the table 15 b and the same values are stored for all WLI-RGB filtercoefficients and NBI-GB filter coefficients (NBI-R filter coefficientsare zeros).

The control circuit 15 sets filter coefficients to be subjected toemphasis processing by the emphasis circuit 48 with reference to thetable 15 b for each observation mode. The table 15 a stores matrixcoefficients of the first matrix circuit 42, the second matrix circuit46 and the third matrix circuit 49 as in the case of the secondembodiment. Matrix calculations similar to those in the secondembodiment are performed.

The configuration in the present modification example is different inemphasized signals but has operations and effects similar to those ofthe third embodiment. That is, since the present modification examplealso performs emphasis processing corresponding to the image pickupdevice with a primary color triple CCD, it is possible to improvereproducibility of blood vessel images or the like through emphasisprocessing in the same way as in the aforementioned third embodiment.Furthermore, use of the image pickup device with a primary color tripleCCD allows an endoscope image with high resolution to be obtained.

Fourth Embodiment

Cases in the WLI mode and the NBI mode have been described in theaforementioned embodiments. The present invention is however not limitedto cases in the WLI mode and the NBI mode as in the aforementionedembodiments, but is also applicable to cases in at least one observationmode of the WLI mode and the NBI mode and a fluorescent mode in whichfluorescent observation is performed. As the fluorescent mode in whichfluorescent observation is performed, fluorescent observation isperformed in a green to red region or a green to near-infrared region.

In the case of this fluorescent mode, emphasized signals are emphasizedas shown in the field of the amount of emphasis according to the imagepickup section (image pickup device) being the complementary colorsingle CCD, primary color single CCD, double CCD or primary color tripleCCD as shown in FIG. 14. In this case, it is also possible to improvereproducibility of the biological mucous membrane while reducing theoccurrence of false color or color moire and acquire an endoscope imageeasy to diagnose.

When the image pickup section is, for example, a primary color singleCCD or double CCD, emphasis processing is performed with respect tocolor signals G and R so that the amount of emphasis of the color signalG is greater than the amount of emphasis of the color signal R.

In this case, as shown in the remarks field, after converting the colorsignals G and R to a luminance signal Y and a color difference signalCr, the emphasis circuit 48 may perform emphasis processing so that theamount of emphasis of the luminance signal Y is greater than the amountof emphasis of the color difference signal Cr.

Furthermore, when the image pickup section is a primary color tripleCCD, emphasis processing is performed on the color signals G and R inthe case of primary color single CCD or double CCD so that the amount ofemphasis of the color signal G is equal to the amount of emphasis of thecolor signal R. Furthermore, in this case, as shown in the remarksfield, after converting the color signals G and R to a luminance signalY and a color difference signal Cr, the emphasis circuit 48 may performemphasis processing so that the amount of emphasis of the luminancesignal Y is equal to the amount of emphasis of the color differencesignal Cr.

Instead of setting the amount of emphasis as shown in FIG. 14 over theentire frequency region, filter coefficients whose amount of emphasis isreduced only in a high-frequency region may be set. In such a case, itis also possible to improve reproducibility of the biological mucousmembrane while reducing the occurrence of false color due to color moireand obtain an endoscope image easy to diagnose.

Furthermore, when images of reflected light of blue color light andfluorescent light of red color light are picked up and endoscope imagesare generated as observed images in the first observation mode in otherobservation modes, emphasized signals may be emphasized according to thecomplementary color single CCD, primary color single CCD, double CCD andtriple CCD as shown in the field of the amount of emphasis as shown inFIG. 15.

Furthermore, as a second observation mode in other observation modes,when an image of blue color light is picked up and an endoscope image isgenerated as an observed image, only one emphasized signal Y or B may beemphasized according to the complementary color single CCD, primarycolor single CCD, double CCD, triple CCD as shown in FIG. 16. In thecase of FIG. 16, since the field of the amount of emphasis indicatingthe relationship of the amount of emphasis with a plurality ofemphasized signals is unnecessary, the item is expressed as “−”.

Furthermore, when an image of red color light is picked up and anendoscope image is generated as an observed image as a third observationmode in other observation modes, emphasized signals may be emphasized asshown in the field of amount of emphasis according to the complementarycolor single CCD, primary color single CCD, double CCD and triple CCD asshown in FIG. 17.

Furthermore, features of incident light, emphasized signal andde-emphasized signal reducing for which the amount of emphasis isreduced or the like in all the aforementioned embodiments can besummarized as shown in FIG. 18.

In FIG. 18, when, for example, incident light on the image pickupsection or illuminating light by illumination means is white, in thecase of a complementary color single CCD or primary color single CCD,the emphasized signal is a luminance signal Y, color difference signalsCr, Cb, a setting is made so as to reduce the amount of emphasis of thecolor difference signals Cr, Cb (with respect to the amount of emphasisof the luminance signal Y) in this case.

The case with a primary color double CCD is the same as the case with acomplementary color single CCD or primary color single CCD on the leftindicated by “←”. Furthermore, in the case of a primary color tripleCCD, emphasized signals are color signals R, G and B, a setting is madeso that there are no signals for which the amount of emphasis is reducedthe amount of emphasis in this case (in other words, set so that theamounts of emphasis of R, G and B signals are the same). Other cases arealso shown using similar notation methods.

When light is described, for example, as blue incident light, the lightmay also be near-ultraviolet incident light. Similarly, when light isdescribed as red incident light, the light may also be near-infraredincident light.

An embodiment configured by partially combining the aforementionedembodiments or the like also belongs to the present invention.

The present invention is not limited to the aforementioned embodiments,but various modifications or alterations can be made without departingfrom the spirit and scope of the present invention.

What is claimed is:
 1. An endoscope apparatus comprising: an imagepickup device equipped with a color separation filter thatcolor-separates and receives returning light of light radiated onto asubject by an illumination device to pick up an image of the subject; anemphasis processing circuit that performs emphasis processing onsharpness of an image signal based on the image pickup device; a storagedevice that stores information for modifying the processing contents ofthe emphasis processing circuit according to a type of the image pickupdevice and spectral characteristics of the returning light incident onthe image pickup device which differ depending on whether a firstobservation mode in which image pickup is performed under illuminationof white light or a second observation mode in which image pickup isperformed under narrow band illumination light; in the secondobservation mode, a first matrix circuit that performs matrixcalculation for generating color signals of G and B from an image signalbased on the image pickup device, and a signal intensity rationcalculation circuit that dynamically calculates a signal intensityration between the G and B color signals based on changes according tothe returning light from the subject in field or frame units in a statewhere a coefficient of the matrix calculation performed by the firstmatrix circuit is set according to the type of the image pickup device;and a control circuit that performs control of modifying the processingcontents of the emphasis processing circuit based on the information ofthe storage device, wherein the storage section stores, when theobservation mode is the first observation mode, first information forsetting an image signal to be subjected to emphasis processing by theemphasis processing circuit to a luminance signal and two colordifference signals, and stores, when the observation mode is the secondobservation mode, second information for setting an image signal to besubjected to emphasis processing by the emphasis processing circuit to aluminance signal and one color difference signal, the first and secondinformation being stored as the information for modifying processingcontents of the emphasis processing circuit, in the first observationmode and the second observation mode, the emphasis processing circuitperforms emphasis processing on the color difference signal in the imagesignal with a smaller emphasis characteristic than on the luminancesignal in the image signal in a frequency domain on a high frequencyside having a higher frequency, and only in the second observation mode,the control circuit performs control to generate the luminance signalwhich reflects the signal intensity ration dynamically calculated by thesignal intensity ration calculation circuit as the luminance signal inthe second observation mode.
 2. The endoscope apparatus according toclaim 1, wherein the storage device stores the first information andsecond information for performing emphasis processing on the luminancesignal and the one color difference signal or the two color differencesignals in the image signal inputted to the emphasis processing circuitusing the different emphasis characteristics according to an arraystructure corresponding to unit pixels of a plurality of filter elementsmaking up the color separation filter and having different transmissioncharacteristics.
 3. The endoscope apparatus according to claim 1,wherein the emphasis processing circuit performs emphasis processing ona specific color difference signal in the image signal with the smalleremphasis characteristic than on the luminance signal in the image signalin a frequency domain on a high frequency side having a higherfrequency.
 4. The endoscope apparatus according to claim 1, wherein theimage pickup device is any one of a single CCD image pickup device, adouble CCD image pickup device and a triple CCD image pickup device. 5.The endoscope apparatus according to claim 1, wherein the image pickupdevice comprises a single CCD image pickup device and the colorseparation filter comprises a complementary color filter.
 6. Theendoscope apparatus according to claim 1, wherein in the secondobservation mode, the control circuit sets the signal intensity ratiobetween the G and B color signals dynamically calculated by the signalintensity ratio calculation circuit as t and u, and controls the matrixcalculation so as to generate the luminance signal reflecting the signalintensity ratio between the G and B color signals by using matrixelements of 0, t and u with a signal intensity ratio of a color signalof R being
 0. 7. The endoscope apparatus according to claim 1, furthercomprising a second matrix circuit for generating second color signalsof R, G and B reflecting the signal intensity ratio from the luminancesignal reflecting the signal intensity ratio dynamically calculated bythe signal intensity ratio calculation circuit and two color differencesignals.